This article was written with the support of the Australian Research Council DP110100175, for which I am grateful. Earlier versions were presented at Bristol, Princeton, San Diego, Uppsala, Dublin, Sheffield, LSE, ANU, Darmstadt, Copenhagen, Melbourne, and Queen's University at Kingston. I am grateful to participants at these events and especially to Chris Armstrong, Anne Barron, Chris Bertram, Garrett Brown, Dan Butt, Amandine Catala, Paige Digeser, Chris Essert, Graham Finlay, Katrin Flikschuh, Bob Goodin, Leigh Jenco, Catherine Lu, David Miller, Margaret Moore, Avia Pasternak, Nic Southwood, Tim Waligore, and Jonathan White for very helpful conversations and comments. I am particularly indebted to Annie Stilz for reading several drafts and to the editor and reviewers of Philosophy & Public Affairs for helping me prepare the final version.